81212989 has 16 divisors (see below), whose sum is σ = 96372864. Its totient is φ = 67464000.

The previous prime is 81212981. The next prime is 81212993. The reversal of 81212989 is 98921218.

81212989 is nontrivially palindromic in base 6.

It is a cyclic number.

It is not a de Polignac number, because 81212989 - 2³ = 81212981 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81212981) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11632 + ... + 17254.

It is an arithmetic number, because the mean of its divisors is an integer number (6023304).

Almost surely, 2^81212989 is an apocalyptic number.

It is an amenable number.

81212989 is a deficient number, since it is larger than the sum of its proper divisors (15159875).

81212989 is a wasteful number, since it uses less digits than its factorization.

81212989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5748.

The product of its digits is 20736, while the sum is 40.

The square root of 81212989 is about 9011.8249539147. The cubic root of 81212989 is about 433.0537778093.

It can be divided in two parts, 812129 and 89, that added together give a palindrome (812218).

The spelling of 81212989 in words is "eighty-one million, two hundred twelve thousand, nine hundred eighty-nine".